Here’s the company’s new explanation of what happens when a user is blocked [emphasis added]:

What happens when a user is blocked?

If you block another user, you will no longer see:

The user in your follower list

Any updates from that user in your Home timeline, including any of their Tweets that were retweeted by accounts you follow

Their @replies or mentions in your Connect tab

Any interactions with that user’s Tweets or account (i.e., favorites, follows or Retweets) in your Interactions or Activity tabs

You will, however, still see this user’s Tweets appear in Search and if you navigate to their profile page.

Note: If your account is public, blocking a user does not prevent that user from following you, interacting with your Tweets, or receiving your updates in their timeline. If your Tweets are protected, blocking the user will cause them to unfollow you.

Have their @replies or mentions show in your mentions tab (although these Tweets may still appear in search).

Follow you.

See your profile picture on their profile page or in their timeline.

Privacy note: If your Tweets are public (i.e., not protected), they will still be visible on your public profile page to anyone, regardless of whether they have a Twitter account or not.

We do not send notification to a user when you block them, but because they will no longer be able to follow you, they may notice that they’ve been blocked.

This is bound to be an unpopular decision, as it seems to benefit trolls more than it does the user on the receiving end. While users always have the option of switching to a protected account, that’s a less-than-ideal solution. Existing blocks should still be in place, but those users can now start following you if they elect to do so.

The one upside to the new policy is that it will be more difficult for users to tell when you’ve blocked them. It’s also worth noting that blocked users have always been able to read the tweets of public accounts since those accounts were… well, public. Now, they can also retweet, fave and follow.

The logic behind this decision baffles me, but it seems like Twitter is moving to have blocking affect inbound instead of outbound actions. That is to say, you can block a user to keep his/her tweets from reaching you, but blocking won’t keep another user from reaching your tweets.

A Twitter spokesperson confirmed with TNW that the change did go into effect today.